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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

VARIEGATED, ORANGE AND BUTLER GLACIERS      119
alluvial fan outside the periphery of the outer bulb. The ice drainage was therefore peculiar, for, on emerging from the glacier it passed first over a lowered part of the glacier which it was burying with its deposits, then through an ice gorge across the outer bulb, building another alluvial fan deposit there. With the development of the interior flat there has probably been a notable decrease in the rate of growth of the outer alluvial fan because so much of the sediment was left by the streams in the interior flat.
The Outer Bulb in 1905. The outer bulb, beyond the interior flat, had the same general features in 1905,1906 and 1909. It rose steeply above the flat to a height of about a hundred feet, and thence to its periphery consisted of an irregular hummocky moraimc mass. For the first half mile or so this moraine had a general black color due to predominance of black hornblende gneiss, though throughout its extent there were scattered fragments of white granite, purple gneiss and other rocks. Outside the black hornblende moraine came a narrow band of red rusted gneiss, then a belt a quarter of a mile or more in width, in which there was such an abundance of white granite fragments among the black hornblende as to give the moraine a grayish appearance when viewed from a distance. In the black hornblende belt there was everywhere distinct evidence of the presence of ice at no great distance beneath the surface, and every here and there ice was seen; but this moraine was much thicker than that on the inner bulb. No ice has been actually observed in the outer belt of white granite moraine, but we are convinced that ice existed there even to the very periphery where the bulb rises above the beach. We reach this conclusion because the moraine surface is cracked, there were areas of slumping, and much cold water was issuing in small streams or standing in shallow lakes. It is even possible that the ice extended out beneath the fiord, for there is here a broad shoal extending at least a quarter of a mile off shore..
On the black hornblende moraine there was a general absence of vegetation, though moss, tufts of grass, and scattered annual plants occurred here and there, and there were occasional young alders and willows, rarely more than one or two years old, though pne was found with ten annual rings. Toward the periphery of the bulb, where the moraine was thicker, the ice thinner, and, therefore, the conditions of stability much greater, the amount of plant growth increased rapidly. On the very outer portion of the moraine were small alder thickets with bushes having usually no more than eight rings of annual growth.
It was evident in 1905 that no ice motion extended across the interior flat to the outer bulb, and, in fact, that there had been no motion in this outer portion of the glacier for a number of years before that. The outer bulb was, therefore, passing through a period of wastage with no addition to its supply, and the inner bulb had started upon the same career, having progressed far enough in it to become almost completely moraine-covered. The condition of 1905 gave reason for believing that both the outer and inner bulbs, together with the interior flat, were on the road to complete destruction by ablation, and had it not been for the spectacular changes of the succeeding year there would doubtless have been little of interest to record about this glacier except the progress of its wastage and the interpretation of its morainic phenomena.
The Advance of 1906. We saw Variegated Glacier for the last time in 1905 about the middle of August, and its condition was then as described above. About ten months later, in June, 1906, when the senior author approached it, he saw, even from a distance, that it was utterly transformed. The outer moraine, outside the interior flat was un-